Conventionally, as a technique of this kind in an excavator and/or a crane, the following techniques have become publicly known:                (i) as disclosed in Japanese Patent Laid-Open No. 2001-41069, when a gate lever for opening and closing a gateway of a cabin is opened, an engine is to be stopped automatically with the determination, based on a signal from a switch adapted to operate in accordance with the opening of the gate lever, that the operator gets off a machine (i.e. the machine is brought into a non-working state); and        (ii) as disclosed in Japanese Patent Laid-Open No. 2000-96627, when a lock lever for inoperably locking a hydraulic circuit is operated, the engine is to be stopped automatically with the determination that the machine is brought into a non-working state.        
However, based only on apparently optimum conditions for stopping the operation, that is, the opening of the gate lever in the above-described known technique (i), and the operation of the lock lever in the above-described known technique (ii), the engine is stopped immediately without considering other conditions, and no follow-up for engine restart, etc. after the stoppage is provided, which causes the following problems in relation to the engine stop:                (A) stopping the engine while performing, for example, a checking and/or repairing operation with an illuminating lamp on may lead to over discharge in the case of using a battery as a power supply;        (B) even though an operator does not intend to stop his/her work, the engine may be stopped unnecessarily; and        (C) it may take the operator, if not familiar with the system, a long time to restart the engine after an automatic engine stop.        
Hence, the present invention has been made to provide a construction machine capable of avoiding the above-described troubles over the automatic engine stop.
To be more concrete, it is an object of the present invention to prevent unnecessary discharge in a machine in which the battery is used as a power supply.
It is another object of the present invention to notify the operator of the coming automatic engine stop to avoid unnecessary engine stop when possible.
It is a further object of the present invention to assist operators unfamiliar with the system to restart the engine.